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Packet PWE3 – Efficient for IP/MPLS

Packet PWE3 – Efficient for IP/MPLS. IeTF78 (Maastricht) – July 25-30 2010 Sriganesh Kini David sinicrope. Problem statement. Need for a packet service that can carry any protocol (similar to an Ethernet pseudowire)

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Packet PWE3 – Efficient for IP/MPLS

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  1. Packet PWE3 – Efficient for IP/MPLS IeTF78 (Maastricht) – July 25-30 2010 Sriganesh Kini David sinicrope

  2. Problem statement • Need for a packet service that can carry any protocol (similar to an Ethernet pseudowire) • Service should be efficient for the most common protocol carried by the service • IP and MPLS are pre-dominant protocols in many deployments • Packet service efficient for IP/MPLS is useful

  3. Service model • Service is modeled as a VPWS that can carry packets of any protocol • Henceforth referred to as Packet Pseudowire (PPW) • Efficient encapsulation defined for PPW over an MPLS PSN • Henceforth referred to as “Packet Pseudowire – Efficient for IP/MPLS” (PPW-EIM)

  4. Network Reference model • A single layer-2 (virtual) circuit is an access circuit (AC) to a PPW-EIM • An AC of a PPW-EIM must not encapsulate another layer-2 circuit. E.g. in a Q-in-Q scenario, S-tag cannot be an AC to a PPW-EIM since it has multiple C-tags

  5. Solution – with Control-Word • CW is used to signal whether the packet is of type - IP, MPLS or ‘other’ • IP and MPLS packets encapsulated in PW without layer-2 header • For non IP/MPLS packets, the layer-2 header is included. The protocol type in the layer-2 header indicates the layer-3 protocol type.

  6. Solution – without CW • Packet following bottom of label-stack is always IP • Since there is a single bottom-of-stack bit in MPLS label stack, MPLS packets don’t need special identification • For non IP/MPLS packets, an IP header encap (GRE) is used for the entire packet (including layer-2 header). A non-routable IP address is used as destination IP address to indicate that packet is non IP/MPLS. • Even if intermediate nodes hash based on IP header there is no re-ordering.

  7. Example: Router interconnect • R1, R2 – routers running LLDP, ISIS on the inter-connecting p2p IP/MPLS interface • PE1, PE2 – PEs providing VLL service using PPW-EIM • IP/MPLS traffic encapsulation in MPLS PSN has no layer-2 header • PE1 and PE2 encapsulate LLDP, ISIS packets (including layer-2 header) into GRE (if no CW is used) or following the CW (when CW is used) R1 R2 MPLS PSN PE2 PE1

  8. conclusion • Lesser bandwidth used. • Fragmentation is reduced for jumbo IP/MPLS packets • Multi-layer network in-efficiency reduced • Enables flow based applications to parse packets efficiently even if there are multiple layers. • This includes ability to do ECMP based on IP (a widely deployed capability today)

  9. v/s draft-balus-pwe3-ip-pseudowire-01 (expired?) • Draft-balus defines operation with CW where ACH encodes protocol type for non IP packets • MAC address configuration may be needed • Fragmentation of non IP packets not possible

  10. v/s draft-bryant-pwe3-packet-pw-03 (virtual ethernet) • Advantages • Lesser bytes on the wire (Bandwidth efficient) • Less chance of fragmentation (throughput efficient) • IP ECMP is possible (even for multi-layer networks) • FAT-PW is not necessary for ECMP • Disadvantages • Not possible to carry layer-2 circuit encapsulated inside a layer-2 circuit • For the no CW case – GRE encapsulation is more involved

  11. Comparison and Next steps • All solutions may have some cases that are not elegant • Optimize for the pre-dominant case even if some complexity is added for a small traffic percentage • Discuss with authors of other drafts and interested individuals

  12. Comments Welcome

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